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Technology to improve soil nutrients

WITH an aim to increase crop yield per acre, farmers often resort to measures that decrease nutrients in the soil.

Soil is the source of mineral nutrients, containing a vast array of organic, inorganic nutrients and gases in different proportion. Plants/crops absorb 16 elements from soil to make its food.

In a situation where soil health is being adversely affected, nutrients are being substituted by synthetic fertilisers. However, fertiliser prices and their quality is still a problem. Furthermore, soil fertility depends on the availability of organic matter. This organic matter not only improves water holding and nutrient retention capacity, but also enhances microbial activity in soil by providing them food. It is imperative for better productivity that our soil should contain enough nutrients. It is a rule for successful and progressive farming that, after removing economical part of plant, the remains should be incorporated in soil.

Presently, wheat is harvested using combine harvester and, consequently, enough amount of dry matter in the form of stubbles remains on the surface of the soil. Usually farmers burn these stubbles which causes environmental issues and loss of nutrients. Burning also affects soil microbes and reduces soil health. This writer (Dr Ehsan Ullah) and his team from the department of agronomy, University of Agriculture, Faisalabad, have devised a system that not only improves soil health but also provides an additional source of income: sowing of sesbania. They have introduced three methods, by which the system could help improve crop production.

Sesbania is leguminous crop that has potential to produce excess biomass in short time with low input requirement. At the end of March/ start of April and when the last irrigation of wheat is completed, sesbania should be introduced at the rate of 10 kg per acre in the standing wheat. It is suggested that the seed should be soaked for 10-15 hours before surface steeping that increases germination speed. At harvest time of wheat, sesbania will grow up to height of one foot and at that time it cannot be ploughed in soil by using simple cultivator.

Sometimes, farmers are unable to sow seed perhaps due to non-availability. They, then have the option of sowing it after wheat harvesting. Primed seeds should be sown after irrigating the area heavily. This way, sesbania will be able to acquire some height before the field is prepared for rice. But the little biomass of sesbania will have improved the soil health immensely.

In this method, seeds are sown at field capacity level (optimum soil moisture level) of soil after wheat harvesting. Weeds may also be grown in this way that can be removed easily. Sesbania can also be sown when farmers have to prepare land.

Two methods are recommended to incorporate sesbania: through rotavator and by puddling method. Rotavator is a better option for which farmers should lightly irrigate the field, then at optimum moisture level, rotavate it. This way, stubbles of wheat and sesbania may be cut down and can be easily incorporated. For puddling, sesbania should be deposited in soil with standing rain water in the core area of rice belt.

This method yields two benefits. Firstly the rovator cuts down plants into small pieces which will start decomposing immediately and, secondly, there will be no need to prepare land further. Soil becomes soft and fertile and this helps in transplanting of rice nursery.

There are a number of benefits of sowing sesbania. For example, with the passage of time, fertiliser requirement dips to half the amount. It also increases soil fertility and when it reacts to the allelochemicals in wheat stubbles, it improves soil health.

Further, nutrients are returned to the soil as against burning wheat stubbles, where 80 per cent nitrogen, 25 per cent phosphorous and 21 per cent potassium is lost. If farmers do not intend to incorporate sesbania in soil they can even harvest the plants and use them as fodder. The method is feasible under all agro-ecological zones and can be adapted with all kinds of soil series.